Thread chaser and chaser assembly



Feb. 2, 1954 T, w, BARNES 2,667,651

THREAD CHASER AND CHASER ASSEMBLY Filed Aug. 22, 1951 33 l7' w. 9W 55 39 250mg @MCL 6:54515 29 45 79 23 6g ama/4% Patented Feb. 2, 1954 y 2,667,651 THREAD CHASER AND CHASER ASSEMBLY Tracy W. Barnes,

to John Ramming Machine Company,

a corporation of Missouri Webster Groves, Mo., assignor St. Louis,

Application August 22, 1951, Serial No. 243,142

11 Claims.

This invention relates to thread chasers and chaser assemblies, and more particularly to tangential chasers and chaser assemblies for use in the die heads of thread cutting apparatus wherein the chasers are made to recede as threading progresses to cut a taper thread.

Among the several objects of the invention may be noted the provision of an improved chaser and chaser assembly which may be economically manufactured with accurately fitting cooperative clamping surfaces of extensive area; the provision of a chaser and chaser assembly allowing for ready insertion, adjustment and removal of the chaser; the provision of a chaser and chaser assembly adapted accurately to hold the adjustment of the chaser under cutting thrust; and the provision of a chaser and chaser assembly allowing for adjustment of the chaser, within limits, to cut threads at diierent tapers.

In general, a chaser of this invention is characterized in having the form of a segment of a cylinder greater than a semicylinder bounded by a plane parallel to the axis of the cylinder, with an axial keyway in the cylindrical part of its surface. The face of the chaser in said bounding plane constitutes a thread cutting face which has serrations extending parallel to the axis of the cylinder substantially throughout the length of the face and being inclined at an angle with respect to the diametrical plane of the keyway, this angle being adapted for cutting tapered threads. The chaser is bevelled at one end to form a cutting edge. The chaser assembly comprises a chaser holder and a clamp associated with the holder having a cylindrical recess formed partly in the holder and partly in the clamp for receiving the chaser. A keyway extends axially of the recess and a key is positioned in the holder and chaser keyways. apparent and in part pointed out hereinafter.

'I'he invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of which will be indicated in the following claims.

In the -accompanying drawing, in which several of various possible embodiments of the invention are illustrated.

Fig. 1 is a plan of a chaser assembly including a chaser;

Other features will be in part` Fig. 2 is a side elevation of Fig. 1;

Fig. 3 is a left end elevation of Fig. 2;

Fig. 4 is a section on lines 4 4 of Figs. 1 and 2;

Fig. 5 is a section on line 5-5 of Fig. l;

Fig. 6 is a side elevation of the chaser per se;

Fig. 7 isa bottom end view of Fig. 6;

Fig. 8 is an axial section on line 8 8 of Fig. 6; and,

Fig. 9 is a view similar to Fig. 5 illustrating a modication.

Similar reference characters indicate correspending parts throughout the several views of the drawings.

Referring to the drawings, a chaser made in accordance with this invention is designated I. As shown, the chaser is of cylindrical form, having a cylindrical clamping surface 3 and a serrated thread cutting side face 5. More particularly, the chaser I consists of a cylindrical tool steel body generally having the form of a segment of .a cylinder greater than a semcylinder cut by a plane parallel to the axis of the cylinder. The face of the body in this cutting plane constitutes the thread cutting face 5 and has serrations extending parallel to the cylinder axis throughout the length of the body. In the cylindrical surface 3 is an axial keyway 1 of uniform depth and extending throughout the length of the chaser. The plane of the cutting face 5 is slightly angled with respect to the diametrical plane of the keyway (see angle A in Fig. 5). This provides a taper angle related to a predetermined thread taper. For example, the angle A may be 1 35 40 for cutting a thread with a standard taper of per foot. It will be understood that chasers with different taper angles may be provided for cutting threads with different tapers.

The chaser may be readily manufactured by milling the keyway l in a length of round tool steel stock, then milling a flat on the stock at the desired taper angle A with respect to the diametrical plane of the keyway, and then cutting axial V-shaped grooves in the flat throughout its length. The resultant flat serrated face is then bevelled as indicated at 9 to provide a throat, with an additional and more inclined bevel at II. In the area of the throat 9, the V-shaped serrations or teeth resulting from the cutting of the grooves are incomplete, increasing in height from the bevel II to a first complete tooth I3 at what is the leading edge of the face 5 as regards the di- 3 rection of movement of the Chaser longitudinally of the work in cutting a thread. The remaining teeth on the face rearward of tooth I3 are also Complete.

One end I5 of the Chaser is bevelled on angle B to provide a cutting edge I'I (Figs. 1 and 6). As best seen in Fig. 8, the face I5 is also at an angle C with respect to the axis of the Chaser to provide not only the desired cutting relief angle, but

pendicular to the diametral plane of the kei/wavy.. n

The bevels B and C are hereinafter ref-.erredto asK being a compound bevel. A tapped hole I'9' extends axially through the other, with a counter-bore 2I at the bevelled end of the chaser.

The holding; -devioez forV the above-described Chaser comprises aholder 2.3l and. a clamp 215=f0r clamping thes'chaser. to the holder... Theclamp is a part. separate from the holder, being; held. to the holder by clamp screws. 21. The holder. is adapted toe beffmountedinv a die head, such asis shown in my copending application entitled Thread Cutting Apparatus, Serial No. 244,659, led August 31, 1951. The die head' includes` wedge parts for inwardand outwardj movement of. ther holder in the. head; these. beingt operative upon sloping surface 'I I. Gradual movement out'- warde. occurs-v. as threading.. progresses in order to cuta taper thread.. Thel holder has an inner end 29,. an outer endv 3|: (at whichv islocated surface 11.)., a iiatface. 33, a fiat baclt facef35,4and; flat parallel sides31.

The-Clamp is mounted on the. frontfaoeV 332 at the inner end. of theholder.- 23. The Chaser.

isv locatedV in a. cylindrical recess.` 39 which is.v s

formed; part-ly in they holder andv partly inthe. clamp.. The cylindrical form of the. recess is the'V same-as'tha-t of the cylindrical clamping surface 3 of the Chaser thusproviding broad-holder: and? clamp areas in clamping engagement with the:- Chaser. for ahigh. degree of rigidity. The-axisof: the recess 353-"A liesin. a plane transverse: to; the'. holder and is. slightly tiltedwith a respect-to. the? back face 3.5 of. the holder; so thatthechaser,V as. mounted' in the holding: device, is orientedatthe: proper helix. angle as1relatedto'the pitclrof the: threadl to be: cut. This helix angle. D isy showna somewhat exaggerated in Fig. 4; Fori example; inthe case'of an Spitchthread; it may be 0 3-1..

Theholder 23 isformed withl a keyway 4I ex-VA tending axially'the length of the recess 39'. A key litA isn held in thiskeyway byscrewg 45. This keyis received in the-.keyway 'I inthechaser; The position of the-keyway' 4 I. and; keyf43" is. suclr that the face; 5 is oriented at the proper taper; angle; With respect to the lengthr of. thework for cuttingf a particular taper thread, beingin a transverse: plane perpendicular tofthe holder. rlfhus when: astraight key 43- is used. as illustratedirr Figs; 2-5,n the plane of the face' 5` generally corresponds to: the previously mentioned taper angle.. Inview of the chaser'being. inclinedvat the helix angle;r and. in. view of the lead angler of the cutting, edge; the: cuttingface is socrientedthat onlythefiirst Com-,- pletetooth I-3- isseiectiveifor thread: cuttingclear4 5 except the first complete;

beveLBmay be-at.an l

the Chaser from oneiendi tot.

. Chaser.. Thead'jiistingscrew the .Clamp-.screws 2.1.

ance being obtained between the remaining Complete teeth and the work so that they serve mainly to Clear out of the thread groove cuttings from the first complete tooth.

Rather than forming the portions of recess 39 in the holder and the clamp separately, it is more convenient and accurate to machine the recess in the assembled holder and clamp. This is best accomplished by inserting a shim between the holder and clamp, tightening the clamp screws 2l, and -then boring the recess in the assembly. It will= be understood thatrthearecesssis bored at theaioresa-id helix angleD. Aflter boring, the recess may be finished by grinding within close limits to the same diameter as the Chaser. The clampr screws arethen loosened and the shim thenrem'oved:

lhaclamp y2.5engages the holder 23 onli7 on afnarrowf-ledge 45. spaced from the end 29 of the holden. with; ai clearance space 49 between the Clamp and holder. from this ledge to the Chaser. It" in this space' that the above-mentioned inserted, the thickness of the shim corresponding to the heighiiof the ledge. The clamp screws, 21. are :.located, betweentheledge. and.; the Chaser..` The Clearancespace. 4A9..allows.for pivot.-V ing. action of. the. clamp. on the. ledge. for rigid. clampingoi-the Chaser... Y

The. recess. 39. has theY form of. asegment of a. cylinder greater than alsemifcylinder. cut-by as plane.. parallehto.- the axisof cylinder correspending,V tof the form of. the` Chaser.. It; is:L open. sidewise at. the. said. plane: at the. end of... the. holder-Clamp. assembly, so. that. there. is a. gall- 5I lengthwise. ontherecess at Whichfthe.thread= cutting. face 5. or theV Chaser` is exposed.` The.. recess. isv Closed at. one. end'. byl an. abutment.y or.. plug. 53, being.A open. at. its :other end.. The Chaser. is. positioned inthe recess.r with. its.. bevellcd. endj I5: at. the open. end of. thezrecess.. ItV isfadi'ustedr astoiitsaxialrpositionf irrthe. recess by.l an.. adiust. ing screw Eli-:threadedirr the tappedhale. I9. with; the end of the screw engagingtheplug.

Adjustment. of.. the. Chaser. is made.. (clamp screwslllloosened.) by. turningthescrew 5.5.Iwhile maintaining itsendin engagementwith theiplug.. Since the. Chaser; is.v held. against turning byithe. key. 43, this results. in; axial. movement. of. the.V 5.5.. has. a .hexagonal socliettf.v in its end. inthe. connterhcre; 2|., of. hole. L91. A. tool. may be readily inserted. inthe. socket'. for turning; the screw.. Whenthechaser has-.been adiusted axially.4 to the. properv position. for. propertangencyA of the. cui'jtingV edge. I1 and the. worin. are .tightenedrigidly to, clampVA thechaser. in position..

The; abutmenavor. plug. 53.' fits in. a, reduced end 59.x of' the recess. 39 andhasaeiangeVA 6I; engag.- ing. ashoulder 53.2.11 theinner end; ofthe.reducedv end. 59. The.. ange.- i's received. in a, groove Sl formed in. the. holder and.; clamp adiacentshoulder.. The. plug. is held.. to the holder by. a. screw 6Fl.. Y V

The.: holder, is also. showni as.. having a.H recess. Ellin its.back...face..35. andthebevel 1.11 at its outer end', 3L.. These, features. are utilized conjunction with.. the; die; head. mechanism disclosed. in` myaforesaid. Copending:l application, but. are not. essential. tos the invention claimed hereiir.. It. will be understood that the. chaser` and: holding; devicemay be usedin. die headsrother than: that disclosediin. said copending, application, and hence. that the holder may be made otherwise. thang hereirrdisclosedssofan as'concernsits cooperation with die head mechanism. f

- Figi 9 shows'how an offset key 13"maly be used instead of the straight key 43 to orient the thread cutting face 5 of the 'chaser at a diierent taper angle from that obtained with a straight key. This within limits enables the same chaser to be used for cutting threads with different tapers and is practical as long as the offset is small. In Fig. 9 the offset is exaggeratedso that it may be readily apparent. n

In the above-described chaser and holding device, the serrations on the thread cutting face of the chaser are' parallel to the chaser axis, and the helix angle Vis"established by the inclination of the chaser axis with respect to the holder (see angle D). It is contemplated, however, that the serrations on the thread cutting face might be made inclined to the chaser axis by the amount of the desired helix angle, and the chaser mounted in the holder with its axis parallel rather than inclined to the back face of the holder. That is, the axis 0f the recess 39 would be made parallel rather than inclined at the helix angle to the back face of the holder, making angle D zero. However, even in this event, the serrations will still extend generally along the chaser axis but at a slight angle equal to D.

The above-described chaser and holding device may be economically manufactured with accurately tting cooperative clamping surfaces of extensive area on the chaser (clamping surface 3) and the holding devices (the cylindrical recess surface 39). This is because a length of round tool steel stock may be readily machined by simple machining operations to form the chaser, and recess 39 may be readily bored in the pre-assembled clamp and holder and with close tolerance m'shed to the diameter of the chaser. A chaser may be readily placed in or removed from the holding device simply by loosening the clamp screws, and may be readily axially adjusted simply by turning the adjusting screw 55. Adjustment of the chaser is accurately maintained under cutting thrust and there is no appreciable tendency for the screw 55 to cant. By using offset keys, the same chaser can be used to cut threads of different tapers.

While I have described the invention particularly as applied to tangential chasers and chaser assemblies for use in receding die heads, it will be understood that the basic principles of the invention may be utilized with respect to formcutting chasers and chaser assemblies such as are used in a standard non-receding die head, wherein the chasers remain xed in position in the die head in making a cutting pass.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A chaser comprising a body generally having the form of a segment of a cylinder greater than a. semicylinder bounded by a plane parallel to the axis of the cylinder and having an axial keyway in its cylindrical portion, the face of the body in the bounding plane constituting a thread cutting face and having serrations extending substantially parallel to the axis of the cylinder throughout a substantial portion of the length of the face, the body being beveled at one end tofo'rm a'utting edge and having" a tapped opening extending therethrough from one end to the other for receiving anadjusting screw.'

2. A chaser as set forth in Vclaim 1,l wherein the bevel at said one end of the body is at a compound angle.

than a semicylinder bounded by a plane parallel to the axis ofthe'cylinder, the body having an axial keyway in the cylindrical part of its surface, the face of the body in said bounding plane constituting a thread cutting face and having serrations extending parallel to the axis of the cylinder substantially throughout the length of the face and being inclined at an angle with respect to the diametrical plane of the keyway. said angle being adapted for cutting tapered threads, the body being bevelled at one end to form a cutting edge.

5. A chaser as set forth in claim 4 further having a tapped hole extending therethrough from one end to the other on the cylinder axis for receiving an adjusting screw.

6. A chaser as set forth in claim 4 wherein the thread cutting face is bevelled to provide a throat portion, with incomplete serrations in the throat portion and complete serrations rearward of the throat.

7. A chaser as set forth in claim 6 wherein the bevel at said one end of the body is at a compound angle.

8. A chaser assembly comprising a holder andi a clamp associated with the holder having a chaser-receiving recess formed partly in the holder and partly in the clamp, the recess having the form of a segment of a cylinder greater than a semicylinder, a keyway extending axially of the recess, a chaser generally having the form of a segment of a cylinder greater than a semicylinder bounded by a plane parallel to the axis of the cylinder and corresponding to the form of the recess and clamped by the cylindrical surface in the recess, the face of the chaser in said bounding plane constituting a thread cutting face having serrations extending parallel t0 the cylindrical axis of the chaser throughout a substantial portion of the length of the face, the chaser being bevelled at one end to form a cutting edge, said chaser having an axial keyway in its cylindrical surface, and a key positioned in said keyways.

9. A chaser assembly comprising a holder and a clamp associated with the holder having a chaser-receiving recess formed partly in the holder and partly in the clamp, the recess having the form of a segment of a cylinder greater than a semicylinder bounded by a plane parallel to the axis of the cylinder and being open sidewise at said plane, said recess having a keyway, an abutment at one end of the recess, the other end of the recess being open, a key extending axially of the recess and located in said keyway, a chaser generally having the form of a segment of a cylinder greater than a semicylinder corresponding to the form of the recess and clamped by its cylindrical surface in the recess, said chaser having a thread cutting face exposed at the sidewise opening of the recess, said thread cutting face having serrations extending parallel to the cylindrical axis of the chaser substantially throughout the length of the face, the

skey, vthe .cha-ser having sa tapped axialholefextending -fromrone Eend to lficha.othein :and an 'adu justing screw threaded in the hole fand having Lits'iend engaging the abutment-,rior rr-aai-xialllylloicat- Aing 'the .chaser .mathe recess.

10. A chaser assembly as set .forthrinfcaim wherein thearecess is inclined-:ata angle im -with espect'to theV homer.

17H. achaser assembly-as A'sxaiifiontl'x claim :9 @wherein the .key has ia :p crtion located 'in .isa-id ikeyway :in vvfame 'recess frand'flan fntset merit-ian located .in the keywa'y in ythe .gehasen TRACY lVST. .-EEARNES.

Rffens Y-Citeil in *me megf 1mg @mem *UNITEDFSTTES PATENTS Number 

